270 PRACTICAL ANATOMY. 



the cardiac plexus ; this plexus, however, transmits the impulse to the nearest 

 somatic nerves, which greatly intensify the pain, and refer the same, peripher- 

 ally, to the chest, left shoulder, forearm, and fingers, by the intercostals, 

 descending branches of the cervical plexus, internal cutaneous, median, ulnar, 

 and radial nerves. Thus, a pain that was reported as simply "aching," in the 

 locality of the lesion, under poor transmissional conditions, becomes, under the 

 better transmissional conditions of somatic nerves, a pain dartijig, stabbing, and 

 excruciating. 



Branches of the Abdominal Aorta and Sympathetic Nerves. I now 

 desire you to dissect the branches of the abdominal aorta with special reference 

 to the sympathetic nerves. This is logical, since the sympathetic accompanies 

 every artery to its visceral end, takes the very name of the artery, and regulates 

 the amount of blood each organ shall receive, both in health and disease. The 

 sympathetic reports to the cortical sensory areas in the cerebrum sensations, both 

 of pain and well-being, through the vagus and all the spinal nerves. It carries 

 on the function of organs during suspension of volition. 



The following explanation of arrangement will give you a clear idea of the 

 meaning of terms. Before you proceed further, master this scheme : 



i. Every artery is surrounded by a plexus of small nerves, which accompany 

 the artery in all its branches to the organ supplied by the artery. 



Sensory N.5* < 



Moto 



6 Sensory Branches of Anterior Crural * -^^ 



) ^>x Patella 



I Motor of Anterior Crural > ^^^^ 



Motor t/ie 7?A ,. 



X face 



FIG. 187. SHOWING SCHEMATICALLY A MOTOR REFLEX CIRCUIT. 



2. This plexus, which always takes the name of the artery it accompanies, 

 has its origin in a ganglion near the beginning of the artery on the aorta ; the 

 plexus also takes the name of the artery which its branches accompany. 



3. The ganglion /. e., all the ganglia situated at the beginning of all the 

 branches of the abdominal aorta is fed by nerves from the solar plexus. 



4. The solar plexus is situated in front of the beginning of the abdominal 

 aorta. It consists of two large semilunar ganglia, which embrace the co-liac 

 axis. The two ganglia are connected both above and below the artery which 

 they embrace. The plexus is formed by branches from the vagus, uniting here 

 with the sympathetic. In this way, then, may be explained the manner in which 

 the vagus reaches all the abdominal organs with motor fibres. 



5. The solar plexus, then, is that part of the sympathetic nerve from which 

 all the abdominal viscera derive their nerve-supply. It is situated high, but is 

 prolonged downward under the name of the aortic plexus. From this the gan- 

 glia situated at the beginning of the branches of the aorta take their origin ; 

 these ganglia throw off plexuses which accompany the artery. The solar plexus 

 is a sort of clearing-house for the abdominal sympathetic nerves. 



6. From above down, then, the succession of names is as follows : (i) '1 he 

 solar plexus, formed of two semilunar ganglia; (2) the dowmvard prolong- 



